consider verifying that `by_group` matches across runs of `prioritise_and_diagnose()` and `analyse()`

[cjyetman]

this

pacta.multi.loanbook/vignettes/cookbook_running_the_analysis.Rmd

Line 146 in 83842f2

- by which variables to group the loan books to produce grouped results of the analysis. This parameter is used across multiple steps of the analysis, both in the diagnostics and in the analysis. This is because it slices and/or aggregates the loan books such that the analysis will produce results along the indicated dimension. If no `by_group` parameter is passed (i.e. `NULL`), all loan books will be aggregated. Otherwise, loan books can either be kept separate (`group_id`) or grouped by any other variable that is provided in each of the raw loan books.

makes me wonder if we should, when running analyse(), verify that the value set for by_group is the same as the value set for by_group in the manifest of the outputs from prioritise_and_diagnose() that are being used. @jacobvjk do you think that is actually necessary? Is that already done, implicitly or otherwise?